Optical fiber connectors (“connectors”) are devices used to optically connect one optical fiber to another, or to connect an optical fiber to another device such as an optical transmitter or an optical receiver. An optical fiber cable typically carries the optical fiber. The connector and the optical fiber cable constitute an optical fiber cable assembly, or just “cable assembly” for short. The connector is typically formed by engaging an inner housing with an outer housing, wherein the inner housing supports a ferrule.
An important property of a connector is its ability to provide an efficient optical connection, i.e., an optical connection whereby the optical loss (also called “insertion loss”) due to the connection is minimal. This efficiency is referred to in the art as the “coupling efficiency.”
Certain types of connectors and connector assemblies are hardened to improve their performance in potentially harsh environments. Thus the term “hardened” describes a connector or receptacle port intended for making an environmentally sealed optical connection suitable for outdoor use. A “non-hardened” connector describes a connector or receptacle port that is not intended for making an environmentally sealed optical connection. Hardened connectors are typically used for FTTX and FTTH applications.
It is advantageous to “tune” the connectors and the cable assemblies in the factory to minimize optical loss in the field. The tuning process involves measuring the core-ferrule concentricity, i.e., the offset between the optical fiber core and the true center of the ferrule in which the optical fiber is supported. In one example, tuning a single fiber optical connector is usually performed by a contact method in which the connector being tuned is mated to a master connector whose fiber core position is known. The tuning can also be performed using other contact methods that do not involve making a connection to a master connector. In other examples, non-contact methods can be employed.
The contact methods that do not involve making a connection to a master connector and the non-contact methods typically require a substantial portion of the outer surface of the ferrule to be exposed. Because the inner housing in most connector designs covers substantially all (e.g., about 90%) of the ferrule length, these measurement methods normally require the core-ferrule concentricity to be measured without the inner housing in place. Accommodating such a requirement in cable assembly processes can add costs, complexities, and/or inefficiencies.